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Sponge + Ferric Chloride Method -- Etch PCBs in One Minute!by TechShopJim on July 12, 2009

Table of Contents

Sponge + Ferric Chloride Method -- Etch PCBs in One Minute! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Intro:   Sponge + Ferric Chloride Method -- Etch PCBs in One Minute! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Step 1:   What You Will Need . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 2:   Clean the Copper and Apply the Resist for the Circuit Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Step 3:   Etch the Board (Instant Gratification!) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Step 4:   Clean Up (Not Much To Do) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Step 5:   Finished Product, and Your Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Related Instructables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Comments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Author:TechShopJim    author's websiteI'm the Founder and Chairman of TechShop.

Intro:  Sponge + Ferric Chloride Method -- Etch PCBs in One Minute!In this Instructable, I will show you how to etch a circuit board with about a tablespoon of ferric chloride etching solution and a 2 inch square sponge. You will beamazed as the exposed copper on the PCB disappears before your eyes, and your board is completely etched in a minute or less!

I found a passing mention of this technique of using a sponge with a small amount of ferric chloride on the Pulsar web site, and I was very skeptical that it could possiblywork. So naturally, I tried it.

Whenever I have made circuit boards in the past, I did it just like most of us do. I put the ferric chloride into a small tub, dropped the masked circuit board into thesolution, and rocked it back and forth for a long time. Even with fresh, strong ferric chloride solution, it would usually take at least 10 minutes for the copper to beremoved. As the solution grew weaker, the etch would take longer and longer.

A few months ago, I discovered the 1-part pool acid (muriatic acid) to 2 parts hydrogen peroxide method of etching a circuit board. You will find lots of wonderfulInstructables on this method. That method works great, and it made me mad that I spent so much money and effort with ferric chloride over the years when I already hadall the chemicals I needed right at home to use this method. The down sides of the acid and hydrogen peroxide solution are that the muriatic acid can cause skin burnsand is a little dangerous and damages things that it contacts. Also, I found the etching solution to be quite aggressive which was great for fast etching, but I ended upwith severe undercutting and partial obliteration of the traces, and the solution tended to be more corrosive to the resist materials I used, and partially dissolved the maskaway during the etch.

This weekend I tried this sponge and ferric chloride method to etch 3 Arduino shield boards I am prototyping for our RFID-enabled member access system at TechShop(TechShop is the 15,000 square foot membership-based DIY workshop with locations in Menlo Park CA, Portland OR and Durham NC). I was so impressed with thesuccess of this technique that I decided to write it up as an Instructable.

The method I will now show you gives you the advantages of all the other methods, and none of the downsides. Specifically:

o You get a fast etch (much faster than either method I know of),o You use a tablespoon of solution, so disposal problems are eliminatedo A small bottle of ferric chloride will last for hundreds of boardso No tank or tub is needed, no heating or agitationo Undercutting is practically non-existent, and the resist stays in placeo There is no need to try to reduce the amount of copper being etchedo The etch is so fast that it is actually exciting to watch and show your friends!

Let's get to it, shall we?

Image Notes1. The circuit board shown is a project I am working on at TechShop...an Arduino shield that is part of our RFID-based member access system for the TechShopworkshop area. I etched the circuit boards with this sponge method.

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Step 1: What You Will NeedYou don't need a lot of supplies for this Instructable, just the following:

o Ferric chloride (available at Radio Shack, 16 oz bottle for $10, part number 276-1535)o Sponge (2" x 2" square, cut from any sponge, or paper towel will work too)o Rubber Gloves (you don't want to stain your hands)o Copper Circuit Board (one or two sided)o Cup of water (to drop the etched board into to stop the etching)

Image Notes1. Ferric Chloride: This common etchant is still available from your local Radio Shack (even though they are moving more towards being a consumer electronicsretailer every day), and from just about any electronics supply house and even suppliers on eBay. Buy ferric chloride solution, and avoid the temptation to buycheaper solid or powdered dry mix. This bottle from Radio Shack is only $10 and with this method will last you pretty much forever.2. Sponge: This one is just a synthetic sponge I cut from a larger kitchen sponge. Keep it thin so you don't have to use as much ferric chloride to saturate it...a littlegoes a LONG way!3. Rubber Gloves: These are just to keep your hands from getting stained yellow from the ferric chloride. They also sort of replace the need for a tank or tub of ferricchloride.4. Cup of Water: This is to drop your etched circuit board into to stop the etching process. You could also just rinse it under a faucet, but I like to do it this way so Ican etch multiple boards in series without getting my gloves wet with the water.5. Copper Circuit Board: This one is just a single-sided scrap that I will use for this Instructable.

Step 2: Clean the Copper and Apply the Resist for the Circuit PatternThere are lots of Instructables about how to apply the circuit pattern onto your copper, including peel and press, photo paper, tape, photo-sensitive emulsions, and evenSharpie pen. I will not touch on that part of the process here, but the method I prefer to use is laser printing onto a piece of Pulsar's dextrin paper and using one of their$70 personal laminators to apply the toner to the board. Then you rinse the paper and PCB under water and the paper slides right off, leaving the toner stuck fast to theboard.

The key to any method of applying the resist is to make sure your copper circuit board is absolutely clean. I use a Scotch Brite pad and some dish detergent to scrub thecopper clean, as shown in the first photo. Then I blot it with paper towel and let it completely dry. Never touch the cleaned copper, because oil from your fingers will causethe resist to not adhere to the copper, and the resist will come off during the etching process.

If you want to play with this Instructable right now and you don't want to make an actual circuit, just use a Sharpie pen to draw a little squiggle onto your cleaned coppercircuit board.

In this case, I laser printed the Instructables robot onto Pulsar paper and applied it to the clean copper board with a laminator. Hey, it came out pretty good!

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Image Notes1. Scotch Brite Pad: Scrub that copper until it shines! Use a few drops or moreof dish detergent to remove any grease and oil.

Image Notes1. Laser printed toner applied to cleaned board. You can use any of a variety oftechniques for creating your resist mask...using Pulsar dextrin-coat paper is onlyone of the many ways but is my favorite.

Step 3: Etch the Board (Instant Gratification!)Put on your rubber gloves.

Open the bottle of ferric chloride and put the sponge over the opening, and tip the bottle to let about a tablespoon or so of solution saturate into the sponge.

Now with the circuit board in the palm of one hand, simply wipe the solution-saturated sponge over the surface of the board over and over. Don't scrub, just keep wiping itall over. In just a few seconds of wiping, you will see the copper start to disappear!

You will find that unlike the submersion etching method, the copper in the center of the board etches away first, so you might want to try to focus on the edges as youwipe.

In less than a minute of continuous gentle wiping, your board will be fully etched before your eyes!

Drop the etched circuit board into the bowl of water to stop the etching action.

If you are etching multiple boards, you can rinse out the sponge, squeeze out most of the water, then re-apply ferric chloride solution if desired, but I have found that I canetch two 2" x 3" boards with one application.

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Image Notes1. Saturate the sponge with only about a tablespoon or less of ferric chloride. Itis astounding how little you actually need, and I didn't believe it until I actuallytried it myself.2. Cleaned copper board with resist applied is ready to be etched.

Image Notes1. Gently wipe the copper with the saturated sponge over and over. You don'tneed to scrub! Sorry about the fuzzy image...it was hard to take the photo withmy iPhone without using my hands, but that's another Instructable.

Image Notes1. After just 15 seconds, the copper in the center is already dissolving away! As Ihold the board up to the light, you can see light through it! If I was using theimmersion method of ferric chloride etching, there's no way it would bedissolving away this quickly! Keep wiping.

Image Notes1. After about 45 seconds, the corners and edges are dissolving away too. Thecopper in the center dissolves first, so try to stay focused with your gentlewiping on the edges and corners.2. I still haven't put any more ferric chloride on the sponge!

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Image Notes1. After 60 seconds of wiping, all the copper is completely dissolved away. Dropthe board into the cup of water to stop the etching action.

Step 4: Clean Up (Not Much To Do)The clean up really is just a matter of rinsing out the sponge, throwing away the rubber gloves (or rinsing them off for reuse), and cleaning any spilled drops of ferricchloride from the work surface.

You can reuse the sponge over and over, so rinse it and let it dry, and keep it with your bottle of ferric chloride.

Image Notes1. Pretty easy clean up! Just toss the gloves away or rinse them for reuse.

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

Step 5: Finished Product, and Your ResultsHere's the finished product. Not too bad for 5 minutes from start to end!

I hope you will agree that this method is faster, cheaper, and more exciting to watch than other etching methods you may have used in the past. I'll bet you'll never usethe ferric chloride tub or tank immersion method again.

I'm not sure if this low-volume wiping method will work with the muriatic acid and hydrogen peroxide etchant, but it is worth a try.

Some information I read indicated that adding a small amount of citric acid to the ferric chloride will make it an even more effective etchant for use with the sponge orimmersion methods. You can find citric acid powder at beer and wine making shops, and even on eBay.

Go ahead and try this sponge method, and let me know in the Comments section if this will become your new method for etching circuits like it did for me.

Related Instructables

How To Make APCB byPARKOUR123

How to make 2-sided PrintedCircuit Boardsby tinygeek

Design a PCBusing a etchmarker andferric chloride.by cliffyd

Printed CircuitBoards (PCB)using the LaserCutter bymashorter

Cheap and EasyToner Transferfor PCB Makingby hilarycheng

Desktop VoltageRegulator/PowerSupply bycousine

Comments

50 comments Add Comment view all 186 comments

 saone says:  Sep 28, 2010. 1:02 PM  REPLYi dont have a laser printer!what can i do?

 TechShopJim says:  Sep 29, 2010. 1:44 PM  REPLYI actually did not use a laser cutter to remove the resist on these boards, but I have on others.

The way I did these boards was with the toner transfer method. They way you do this is as follows:

o Design your circuit and print it backwards with a laser printer onto photo ink jet paper or special paper made by PulsarFX(http://www.pulsarprofx.com/pcbfx/main_site/pages/products/transfer_paper/transfer_paper.html)

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

o Place the printout face down onto super cleaned scrubbed copper clad PC board

o Use a clothes iron or laminator to heat the printout and the board, and the toner will be remelted and will stick to the copper board

o Put the paper and copper board under warm water and allow the paper to soften (if you are using dextrin coated paper, it will slip right off). This stepwill leave the only toner on your copper board with no paper.

o Now you can etch the board with ferric chloride or peroxide/hydrochloric acid etchant.

I plan to write up this article as an Instructable sometime.

Good luck!

 saone says:  Nov 5, 2010. 1:47 AM  REPLYi DON'T own a laser printer....is there any other solution?like printing it with regural injekt printer or just go that circuit photo to a photograph center-shop and let them print it for me?

 trueblackdragon says:  Feb 27, 2011. 7:29 PM  REPLYyes you can use photo resist boards or make your own using the same solution used in silk screen printing. then you can buy inkjet transparencypapers from almost any office supply, expose to light per directions then wash with water. have fun etching!

 townsend1212 says:  Nov 21, 2010. 11:08 AM  REPLYYes I go to Kinko/Fedex center and make the copies myself. I asked them to do it but it was over the heads a little.?? No problem for you though.

 hintss says:  Nov 4, 2010. 6:42 PM  REPLYhe dosen't have a laser printer. print with the inkjet, then go to kinkos and have them copy it.

 SniperProf says:  Feb 19, 2011. 9:40 PM  REPLYVery nice :)

 greengraff says:  Feb 6, 2011. 4:37 PM  REPLYcan i use permanent marker pen in covering the pcb???/

 TechShopJim says:  Feb 7, 2011. 12:17 PM  REPLYYes you can. They make special resist pens that have a thicker ink, but Sharpies will work. Also, I have used waterproof india ink or waterproof ink fortechnical pens. There are pens called Rapidograph pens that work very well.

 cold.geek says:  Jul 14, 2009. 3:15 PM  REPLYYou've just rinsed copper chloride out of the sponge and down the sink, which means you've not eliminated the disposal problem but you've ignored it. Themain issue in the disposal problem isn't because of the the large amount of Ferric chloride that doesn't react with the copper, but the small amount of it thatdoes.

 dawning says:  Jan 10, 2011. 9:05 AM  REPLYIndeed and I'd worry that the Ferric Chloride solution isn't fully reacted.. Which, in draining through my pipes, of which some of my plumbing is copper..well.. yeah... No thanks.

Where I live the local firehall will take whatever chemicals. You just drive them over in an onimous container and they'll add it to a big pile of mysteriousthings.

 naughtyhorse says:  Feb 3, 2011. 5:31 AM  REPLYcopper used in drainage?good lord :-)all mine's pvc

 Jimmy Proton says:  Dec 30, 2010. 4:24 PM  REPLYA little bit on a sponge will quickly be diluted in the water and wont harm anything.

 worldgnat says:  Jul 16, 2009. 8:04 AM  REPLYSo what is the best way to dispose of the resulting solution? I'm sure it varies from place to place, but is there a site where one can look these things up?

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

 theblindferrengi says:  Mar 11, 2010. 7:22 PM  REPLYThis is what the MSDS sheet says about disposal:

"Disposal Considerations

Whatever cannot be saved for recovery or recycling should be managed in an appropriate and approved waste facility. Although not a listed RCRAhazardous waste, this material may exhibit one or more characteristics of a hazardous waste and require appropriate analysis to determine specificdisposal requirements. Processing, use or contamination of this product may change the waste management options. State and local disposalregulations may differ from federal disposal regulations. Dispose of container and unused contents in accordance with federal, state and localrequirements. "

Its not much help, but I would take it to a landfill on one of their hazmat days, although its not illegal to dump it.

 hinge says:  Jul 13, 2010. 6:39 AM  REPLYyou can mix the etchant(+ pieces of used sponge) with a baking soda solution-any concentration 3-5% will do.You end up with a mixture ofundefined iron hydroxides and table salt solution.Should be less aggressive than FeCl3 and possible to flush down the drain.

 JTomM129 says:  Dec 16, 2010. 1:21 PM  REPLYSounds like a good compromise . . .

That said don't forget you are using a tiny fraction of the FeCl3 solution that the "traditional" method calls for per. PCB (and I bet lots of thatsolution goes guess where?). Also, the small amount of solution that is used using this method gets diluted many times over will probably noteffect house pipes to any measurable degree. Just flush with lots of rinse water after each session.

 rykonen says:  Mar 22, 2010. 1:45 AM  REPLYIf Ford can continue to make cars, I think the earth won't mind a bit of used and diluted ferric chloride.  Am I the only one here who feels this way?

 Absinthemadness says:  Sep 13, 2010. 11:09 AM  REPLYI would hope so.

 Arex_x says:  May 31, 2010. 6:31 AM  REPLYNo.You should always be careful about what you put down the drain. But ...well , I don`t know really.I see what you`re saying , about this being a small source of copper into the nature. And I think it is.But it could have been interesting to do some math on it, sometime : )

 beehard44 says:  Aug 18, 2010. 7:54 AM  REPLY....and down the drain it goes!

thats what i think when i pour stuff (harmful) down the drain

 hintss says:  Nov 4, 2010. 6:44 PM  REPLYjust like the 5 microscope coverslips I broke in science a month ago. It ended up clogging the drain.

 tgrundle says:  Dec 9, 2010. 7:39 AM  REPLYI think some of you may be missing another important point here (even a year and a half later). This stuff attacks copper and theplastic the circuit board is made of. No mater if you have a newer or older home this stuff could attack your pipes. I don't thinkanyone wants to waste several days digging up and replacing pipe when we could be etching circuit boards!!! :)

 GitarGr8 says:  Dec 20, 2010. 7:47 PM  REPLYCopper drain pipes? Not very likely, even old sewer lines are typically made of clay, newer lines are usually ABS or perhapsPVC plastic. The reason people are / should be concerned with the proper disposal is because elevated levels of copper in abody of water is harmful to the fishies.

 TechShopJim says:  Dec 20, 2010. 10:21 PM  REPLY

The thing about all this is...when you flush material down the drain, it DOES NOT go into your local lake, stream, river, orocean! It goes to your community's waste water treatment plant. They precipitate out the metals (it is valuable to them),and the even use ferric chloride in the treatment process!

So unless you live on a boat and you dump your waste at sea, or you live in the back woods of some remote location andyour sink and toilet pipes drain directly into the creek, your use of ferric chloride to etch circuit boards is NOT going to hutany aquatic life!

The people in your neighborhood collectively put more copper into the water system (from the copper cladding on the zincpennies wearing down in their pocket and then laundering their pants) than you every will by etching circuit boards athome.

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

 GitarGr8 says:  Dec 21, 2010. 9:38 AM  REPLYThat's like saying it's okay to dump your motor oil down the drain because the sewer treatment plant has an oilskimmer. What about people with septic tanks? People also tend to dump stuff in other places than the sink. Whatabout storm drains? They lead straight to the ocean in my area. I just think it's irresponsible to tell people it's okay todump materials that should be disposed of properly.

 worldgnat says:  Dec 9, 2010. 9:07 AM  REPLYAnyone have any thoughts on sodium hydroxide? Mixing it at three times the concentration of the ferric chloride should yieldsodium chloride solution and ferric hydroxide precipitate, neither of which is that harmful (ok, so ferric chloride is an irritant, butit's not as dangerous as ferric chloride by a long shot.) The reaction will be violent, but done in sufficiently low concentrations(maybe <1M,) it shouldn't be too bad.

Am I missing something huge here, or is this a good idea?

 greengraff says:  Dec 14, 2010. 10:39 PM  REPLYcan i use another brand of ferric chloride?

 TechShopJim says:  Dec 14, 2010. 11:11 PM  REPLYYes. Ferric chloride is just a chemical compound, so it doesn't matter which brand you use. Radio Shack is just the most convenient brand for mostpeople in the United States.

You can get ferric chloride on eBay in powder form for about $20 USD per pound including shipping. The powder is mixed with water to reconstitute it foruse.

 janw says:  Dec 12, 2010. 5:32 AM  REPLYgreat instructable!

 Mak5 says:  Dec 11, 2010. 1:33 PM  REPLYGreat work man!

Sorry, maybe I missed it, how do you get the resist off the finished product so the copper is exposed?

Thanks

 TechShopJim says:  Dec 11, 2010. 9:15 PM  REPLYAcetone!

 Foxtrot70 says:  Dec 9, 2010. 6:54 PM  REPLYI like your Instructable, EXCELLENT! I found a laminator at Harbor Freight for $29.99 here is the link

http://www.harborfreight.com/catalogsearch/result?category=&q=laminator

I have battles for years with the baths etc to make boards this is cool.

 gel. says:  Dec 6, 2010. 9:06 PM  REPLYWow. A lot of comments! I have one question to ask since I really don't have time to go through the 150+ comments.

I'm doing a lot smaller work. I was wondering if you had any experiences with using a q-tip to apply the etchant instead of a sponge. It would be a lot neaterfor me and easily disposable!

 TechShopJim says:  Dec 8, 2010. 1:01 PM  REPLY

Hi Gel...

No I haven't, but I'd like to try it. I think it might work very well, since the idea is NOT to scrub at all, but just disturb the loose oxidized layer on the copperformed by the ferric chloride.

I'm also testing some methods of using one of our many Epilog 60-watt laser cutters at TechShop (at our Menlo Park location or our brand newdowntown San Francisco location that just opened Monday...plug plug!) to produce the resist layer. In my research over the last couple of weeks, Iaccidentally stumbled across some very interesting techniques for doing slip casting of ceramic materials and glass powder using a laser cutter andacrylic sheet...I'll have those posted as Instructables soon!

 townsend1212 says:  Sep 13, 2010. 1:49 PM  REPLYYou can't get ferric chloride from Radio Shack any longer

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

 punkhead58 says:  Oct 8, 2010. 5:54 PM  REPLYI thought the same thing. I searched every RadioShack in my area for months looking for it, and none of them had any in stock. But last week, I wentthere just to buy some LEDs and they had it again! Check your local store before they run out again!

 TechShopJim says:  Sep 13, 2010. 2:30 PM  REPLYOn the Radio Shack web site, all the Radio Shack locations listed near my house all indicate that they have it in stock. What ZIP code are you in (if youare in the US)?

 townsend1212 says:  Sep 14, 2010. 10:23 AM  REPLYWell is my face red. I guess 'ferric chloride' is an unknown at Radio Shack as it is burried in the 'PCB etchant' description. Instructales is good but Ineeded a little frogging around before I got what I wanted, I hope. I think I have the info now. Anyway I am trying the muratic acid and hydrogenperoxide formulae.I am plating copper to brass then masking and ectching off the copper and a little brass to make a name plate for my product. I may even do anInstructable.

Thanks to you all.

 TechShopJim says:  Sep 14, 2010. 1:22 PM  REPLYOK, good. You scared me. Radio Shack used to carry TONS of hobbyist supplies, and now they are down to a small handful (TechShop locationswill carry more hobbyist supplies than Radio Shack!)

Ooh, that's a cool idea, though. That makes me wonder about copper plating other metals that are NOT attacked by ferric chloride, and thenetching off the masked copper.

What metals are NOT attacked by ferric chloride, and which metals are NOT attacked by peroxide/acid etchant?

 Rock D says:  Sep 30, 2010. 10:27 PM  REPLYi cant find fecl3 solution here by around my city. they offers me a crystals of fecl3. so help me to make solution of that????

 TechShopJim says:  Oct 1, 2010. 10:11 AM  REPLYYes, that will work. You just mix it with water to activate it.

Remember the safety rule: "Add acid to water, just like you ought'er."

That means you put the water in the container, and slowly add the FeCl3 powder to the water. NEVER do it the other way around...for example, NEVERpour water into a container of acid or other chemical because it could heat the water and burst into steam and kick the chemical up into your face.

Enjoy!

 eggman says:  Aug 23, 2010. 3:47 PM  REPLYi used this method using toner transfer and a cotton ball instead of a sponge, worked beautifully. i found that the sponge i was using was far too rough for thejob the first time i tried it though, but the cotton ball solved all of those problems.

 TechShopJim says:  Aug 23, 2010. 4:09 PM  REPLYHi EggMan... That's a great idea...cotton ball! Did you find that the cotton fibers would get caught up on the edge of the copper layer? Thank you!

 eggman says:  Aug 23, 2010. 5:09 PM  REPLYwhen the cotton is soaked in ferric chloride, it gets a little denser, and it didnt catch on anything.

 jeff-o says:  Jun 4, 2010. 8:31 PM  REPLYI just used this method to make a board. It was indeed faster than simply dropping it in a vat of ferric chloride, but not quite as fast as it seemed to take foryou! Also, I needed to refresh the ferric chloride in my sponge a few times for each side of my board, because it was becoming saturated. Indeed, when Isqueezed out the sponge, there was a lot of black and a lot of bright green; indicating the solution was saturated with copper.

 TeslaFreakshow says:  May 25, 2010. 11:39 AM  REPLYI tried this last night and it was far worse than just using the ferric chloride the normal way. After 20 min I had a half etched pcb and my resist was abouthalfway gone even if I had finished etching the board would have been useless.

 TechShopJim says:  May 26, 2010. 2:29 PM  REPLYI'm sorry it didn't work for you.  Everyone I have talked to who uses this method at TechShop absolutely LOVES it...so I'm not sure what you might bedoing that is different.

We use 1/2 oz copper...maybe you were using 1 oz or 2 oz?

We generally use toner as a resist...what resist are you using?  Sharpie pens as resist don't hold up very well.

How hard are you scrubbing?  You don't need to scrub at all...just light wiping to stir up the etching solution on the surface of the copper.

Thanks!

http://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/

 TeslaFreakshow says:  May 26, 2010. 4:09 PM  REPLYI was using 1oz copper and toner resist. I wasn't really scrubbing it just wiping but it was taking so long. Probably would have been done in 10 minwith 1/2 ounce since it was about halfway etched. I ended up re etching a new board using hcl and peroxide. No loss though etching at home is allabout trial and error. Maybe I'm just impatient.

 vmspionage says:  Jul 16, 2009. 7:24 AM  REPLYHmmm, I wonder if I can use the sponge method with UV resist and ammonium persulfate... I'll give it a shot and let you know!

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